I am often asked this question and the short answer is that a hearing (or induction)loop makes communication easier for hearing aid users. It can increase comprehension from 0 - 10% to as much as 90%.
People with hearing loss may find it difficult to hear the spoken word in places where there is ambient noise or poor room acoustics, e.g. shops, supermarkets, cinemas, theatres and meeting rooms.
An audio frequency induction loop (AFIL) provides a magnetic signal that is picked up by a hearing aid when it is set to it's T (Telecoil) setting.
A loop system will have:
A microphone to capture the spoken word,
An induction loop amplifier to process the audio signal,
A loop cable covering a specific area to act as an aerial (creating the magnetic signal required by the hearing aid)
In order to let hearing aid users know that a loop is installed, standard T loop signs should be provided.
There are different hearing loops for different situations, e.g counter loops or room loops.
For more information:
IEC 60118-4 2014 covers system performance requirements
IEC 62489-1 2010 covers methods of measuring and specifying the performance of system components
BS 7594 1993 is the Code of Practice for audio frequency induction loop systems (AFILS)
Institute of Sound and Communication Engineers - www.isce.org.uk